Army ant week: Biologist and photographer Alex Wild reported on army ants all last week in a series of posts on his blog Myrmecos. In one post, he described how army ants link with one another using hooks on their feet: “When the time comes to encamp, they can string together living curtains of ants in a matter of minutes. Army ant bivouacs are made from the ants themselves, a vibrant structure that protects the vulnerable brood and...

Male jumping spiders (Phidippus clarus) size one another up before engaging in a fight—whether the aggression is based on rights to mating or territory—and in many cases, the pre-fight displays are sufficient to deter physical contact. The males do not nest but instead wander between female nests looking for opportunities to mate. The females, on the other hand, are not nomads—they build nests from silk and leaves in which they wait while they draw closer to sexual maturity.